The present invention relates to a new motor system, and in particular, to a constant-power brushless DC motor, which is effective in energy saving, has good characteristic of speed conversion from a low speed to a high speed, has no torque ripple, produces high power with a low voltage, has excellent stable speed characteristic and high efficiency, has compact configuration not to require a cooling system, and is able to be fabricated in full automation with low production cost.
A conventional DC motor has problems that its brush and commutator are worn with the lapse of time, its configuration is complicated, and requires a high production cost. Especially, it is difficult to obtain a high speed of above 6000 rpm using a conventional power motor. With an AC inverter motor, its start torque is weak, controller needs high cost, and constant-power cannot be produced. Furthermore, a reluctance motor is inferior to other motors in terms of fabrication cost, size and weight, and does not produce constant-power. In general, a brushless DC. motor is widely used as a small-sized motor. However, it is difficult to fabricate the surface of permanent on which a rotor is set, its controller carries out four-quadrant control, requiring high cost, and constant-power cannot be produced. Moreover, the brushless DC motor cannot completely solve problems of nonuniform rotation, torque ripple and heat generation.
Accordingly, the present invention is directed to a constant-power brushless DC motor that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a constant-power brushless DC motor, which has no torque ripple, produces high power with a low voltage, has excellent stable speed characteristic and high efficiency, has compact configuration not to require a cooling system, and is able to be fabricated in full automation with low production cost.
To accomplish the object of the present invention, there is provided a constant-power brushless DC motor, including: a stator which is wound in parallel by phases and polarities and configured of n multi-phases, each of the winding coils of the stator which are not connected with one another is connected to each of n full H-bridges, n full H-bridges are connected to a DC power supply in parallel; a rotor having a predetermined number of polarities, which is required to concentrate magnetic flux on its area; a commutation encoder including sensing regions and nonsensing regions, the commutation encoder being externally set to one side of the shaft of the rotor; and two photo sensors set to each phase, the two photo sensors being connected to half H-bridge of each phase, to turn on/off the half H-bridge, the distance between the sensing regions of the commutator encoder is determined to allow a phases among n phases to be excited all the time, the a photo sensors recognizing the a phases excited.
It is preferable that the stator has narrow slots to remove cancel phenomenon. The number of phase among the n phases, which will be excited, is determined by the distance between the sensing regions, the distance between the sensing regions being determined through the following expression,
distance between sensing regions=(2Πxc3x97number of phases to be excited)/(number of polarities of rotorxc3x97number of phases of motor) (xc2x0)
the number of sensing regions in the commutation encoder being determined through the following expression,
number of sensing regions=(number of polarities of rotor)/2
the distance between the photo sensors on a sensor plate being determined by the following expression,
distance between photo sensors=2xc3x8/(number of polarities of rotorxc3x97number of phases of motor) (xc2x0)
among the n phases, a phases being excited but b phases not being excited all the time. It is preferable that bxe2x89xa71, b corresponding to the number of phases inexcited.
The constant-power brushless DC motor of the present invention, which has multi-phases of 2, 3, 4, 5, 6, . . . , n phases, is configured of 1, 2, 3, 4, 5, . . . , a phases excited and 1, 2, 3, 4, 5, . . . , b phases inexcited, to alternate the excited phases and inexcited phases, being started and rotated. The rotor is configured of a permanent magnet, the stator is configured of independent winding in multi-phases, and the commutation encoder is externally fixed to one side of the shaft of the rotor to be rotated. The n phases include 2n sensors which are connected to the switching stage to sense the location of the rotor, indicating the direction and interval of current, thereby starting and rotating the motor. The stator, rotor, sensors and controller are constructed to be automatically fabricated, reducing the manufacture cost.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.